Skip to main content

How to Convert a Glock 21 to .45 Super


Safety First!

If you're reading this, chances are you know what a .45 ACP cartridge is, as well as a .45 Super cartridge, and are interested in how to modify your Glock to fire .45 Super. If you don't, check out this article on the .45 Super. That is all well and good, and easily possible, with a bit of time and research. There are just a few things to note, before we get started.

First, remember that many .45 Caliber handguns, especially older ones, are not built to withstand the increased pressures and stresses of the .45 Super cartridge. We will be working with Glock, which can withstand such, but not without certain modifications. Use of an improperly set up weapon can and will hurt the weapon and you.

Secondly, remember that even if a weapon can withstand the shock of firing a more powerful round, they are not designed for it. Increased wear and tear will occur, especially if you intent to fire .45 Super out of it on a regular basis.

Thirdly, keep in mind that THIS WILL VOID THE WARRANTY. Glock will not be happy that you have modified their weapon, and if any damages occur to the weapon, they will not fix it for you.

DISCLAIMER: I have done research on my own, and have every reason to have confidence in the information provided here. However, neither I, nor Hubpages, may be held responsible for any damages caused to yourself, or to your firearm. Yes, this is the "cover my own rear" section. I carry one of these weapons myself, every time I go out the door, and have complete faith in it.

What You Will Need

There are a number of places you can find information on the .45 Super cartridge, and .45 Super conversions. In fact, the first search term will bring you to Ace Custom 45's website. They sell a "conversion kit" for the Glock 21 to allow it to safely fire .45 Super. If you purchase their kit, which sells for a hair under $400, you will indeed be able to fire .45 Super safely out of your Glock 21. You'll also have such improvements as an extra power magazine spring, a Pearce Glock grip enhancer,and a Jentra Glock grip plug nose, none of which you need to fire .45 Super. They also demand that you have the slide ported by a company of their choosing.

Now, it goes without saying, you don't need all of this. You can buy your own grip enhancer and plug from a dealer of your choosing, at a time of your choosing. The magazine spring, I have never once needed thus far. Porting is another issue altogether. It will reduce wear and tear on the frame, as well as felt recoil. it will also render it less effective as a defense weapon, causing blindness at night, and possibly burning you with hot gasses if you have to draw from retention to protect yourself.

If you simply want to convert your Glock to .45 Super, with out all the frills attached, here is what you will need:

Performance Barrel

You may be thinking "Oh, my stock Glock barrel can handle this round just fine, I don't need to purchase a new one." You might also be right, but I would point out one thing. Glock's barrels do not fully support the shell casing of .45 ACP rounds; the cartridge hangs over the edge of the feed ramp, leaving an area of unsupported shell. Do you really want a cartridge with that much more power unsupported in any way, when the result could be the destruction of your firearm?

Stock Glock barrel with unsupported portion.

Stock Glock barrel with unsupported portion.

Which Barrel Should I buy?

There are several companies with fantastic reputations to purchase from, and all of them will have great performance. The largest deciding factors are price and looks. These are a few of the options:

  1. KKM Precision: 416 stainless steel. 42 -45 RC. Button Rifled. Threading and 6" options. Base Price: $165.00
  2. Storm Lake: 416 stainless steel. 40-42 RC. Cut broach rifled. Steel or Black color options; 6" or threaded barrel options. Base Price: $160.00
  3. Bar-sto: Cut Broach Rifled. Available to be match fitted. Base Price: $215:00
  4. Jarvis: 4140 weapon steel. 40-44 RC. Available to be match fitted. Base Price: $200.00
  5. Lone Wolf Distributors: 416 stainless steel. Cut broach rifled. Lifetime warrenty. Base Price $109.95
  6. EFK Fire Dragon: 416 stainless steel barrel. Threaded or un-threaded. - Price:$150.99 / 220.00 Threaded

What you choose will depend on what you like, and what you intend to use it for. I personally have a KKM Precision standard 4.60" barrel. Lone Wolf Distributors is a good, affordable option, if you can stomach the silly wolf icon they insist on scrawling on the top of the breechblock. I believe you can pay them to put it underneath, where it isn't visible, and still come out on top. I would also highly recommend Storm Lake, as they offer a black finish, if you can wait 30 days for it.

Personally, I would stay away from EFK Fire Dragon, as I have heard mixed to bad things about the company and its support, including one horror story about the quality of a barrel made by them.

KKM Precision Barrel with fully supported chamber.

KKM Precision Barrel with fully supported chamber.

Stainless steel guide rod with 24 pound recoil spring.

Stainless steel guide rod with 24 pound recoil spring.

Aftermarket Guide Rod and Spring Assembly

3rd generation and previous Glock 21s have a single plastic guide rod and 17 pound recoil spring in them. Firing .45 Super rounds out of a Glock with a stock 17 pound recoil spring would have the slide slamming into the frame with great force with each pull of the trigger. I'm not sure how long it would take to damage the gun irreparably, but I know I wouldn't want to be the one who's Glock was used to test it.

To remedy this, the solution is simple. You have to replace the recoil spring. In Glocks, the guide rod is permanently attached to the spring, it is a captive, non-separable assembly. That means that while you're at it, you might as well buy a stainless steel guide rod. The stock plastic ones reek of cheap and flimsy, in my opinion, anyway.

You'll need a recoil spring rated at anywhere from 22 to 26 pounds. Personally, I chose 24, because I can still fire .45 ACP without any reliability issues with it, but if you're intending it to be .45 Super only, I'd recommend 25 or 26.

Scroll to Continue

You can buy recoil springs and guide rod assemblies from almost anywhere, and they tend to be reliable. Personally, I chose a Lone Wolf captive guide rod, with ISMI recoil spring. You can find both of those at Lone Wolf Distributing's own website. Make sure, if you choose a captive guide rod assembly, to put some Loctite or similar product on the screw. It won't do anyone any favors if your guide rod comes apart while the weapon is being fired.

Glock 21: Chambered for .45 ACP/.45 Super

Yes, its that simple. A drop in barrel, and a new guide rod and spring assembly. Once you have your fully supported barrel, and guide rod and spring assembly, simply assemble them as necessary, and drop them into your Glock, and viola, you can now shoot .45 Super cartridges. Remember, before you drop the parts in, to clean and oil them. You don't want any dirt or debris picked up during shipping to make it into your Glock.

Below is a picture of my own Glock 21, modified to shoot .45 Super. It is my Everyday Carry weapon, and it has run about 500 .45 Super rounds through it with no difficulties and no noticeable damage, wear, or tear. Your mileage may vary.

My 3rd Generation Glock 21, with .45 Super modifications.

My 3rd Generation Glock 21, with .45 Super modifications.

As always, thanks for reading. I hope someone out there found this helpful. Feel free to drop me a comment if you thought it was helpful, horrible, or simply wanted to make a correction to something I've said.


Howard on December 17, 2019:

I use Blue Bullets coated 230gr RN bullets, 6.0 gr bullseye powder, overall length 1.225 inch, starline brass from Midway.

5.2 inch threaded lone wolf barrel.

Estimated brass 25.5 gr water.

Quickload estimayes:

1023 fps

26564 psi

81.3% burn rate (low flash)

Use yankee hill Compensator and 22 pound recoil spring.

I have decided that i like 10mm better.

No compensator necezsary for reluable operation.

Underwood 200 gr FMJ, and hornady critical defense, and my reloads all function perfectly with glock 20 slide on my glock21 using 24 pound recoil spring. The heavy recoil is probably not necessary, but it makes me feel safer using the full power underwood ammunition.

So, one can carry one mag with critucal defense, and a second mag with underwood should circumstances require maximum penetration.

greg yonai on November 27, 2019:

thanks Tom for your input. Question is what are your 45 super ammo loads, bullet weight, bullet diameter and velocity. I have ordered a tungsten guide rod with 22 lb spring from Glock store. I DO RELOAD But for now, I purchased some underwood 255 grain hard cast to try after I CONVERT MY GLOCK 21. I ordered 500 45 super brass from Starline and now I NEED TO FIND AN APPROPIATE bullet. Any recommendations on bullet weight, diameter and c.o.l. thanks


Mike on January 15, 2019:

I thought it was a very informative issue. Thanks for

The info. I think I'm going to convert my gen 3 as you did with yours.

William Hutton on June 16, 2018:

I have a glock 41 with a KKM barrel of I get a heavier recoil spring and stainless guide rod would it be fine for occasional 45 super loads thanks

OSCAR APARICIO on May 27, 2018:

I love your article. I just order all the parts for my glock 21 to converted. I was to use to 45 super as my back up gun for hunting hogs and for any bear defence

Howard on March 24, 2018:

I tried a 22 pound spring with YHM compensator.. The factory 45 ammo and my reloads worked fine. However my 45 super reloads jammed with slide open on last round in magazine. This happened in 3 out of 3 tests with 13 round magazine. With my 10 round magazine, no problems at all with 45 super.

Last year I replaced all the magazine springs with new springs purchased directly from glock. I like the YHM compensator because it is a two piece design which does not require locktite, and easily goes on and comes off without tools.

So my conclusion is:

if planning on shooting 45 super use the 24 pound spring with YHM compensator.

For 45 acp, use 22 pound spring with YHM compensator, or any spring from factory 17 pound to 24 pound spring without compensator.

For 45 acp and 45 super, use 22 pound spring with YHM compensator, but will need extra strong magazine spring to avoid last round jam. Or just accept the likelihood of a jam with the last round in the magazine.

Howard on December 20, 2017:

I found that with barrel change and 24 lb recoil spring, that it the G21 would not reliably chamber the last 3 rounds from the magazine.

Installing a yankee hill machine compensator on the threaded barrel solved this problem (slows down the slide), and had good functioning with my 45 Super reloads.

However, my regular 45ACp reloads would not reliably function.

I'd like the G21 to work with both 45ACP and 45Super without changing any parts. So, next I plan on trying a 22 lb recoil spring.

Normanrea on May 14, 2017:

Thanks. I found your article very informative. I'm a 45 acp nut.


TomBlalock (author) from Hickory, NC on February 11, 2014:

Understandable. Hydra-shok isn't bad, in all honesty, but it does have a pretty massive tendency to get clogged by clothing and become a glorified round nose, but a bullet in the body is still a bullet in the body. I wouldn't be the one wanting to get shot by it, one way or another. Then again, I hadn't planned on getting into any running gunfights with police, either. Typically bad for one's health.

j Michigan on February 10, 2014:

The reason why i know about the perp having 8 rounds in him and one through heart was from the autopsy report although i was quite confident my rounds were hitting their mark. When he stood up i only fired one more round which was a headshot an inch above his left eye. I know now he would have breathed his last from the heart shot on a few more seconds but those are crucial considering he had 3 more 9 X 21 rounds left.

j Michigan on February 10, 2014:

We are now permitted to carry glock 9mm, 40, ot 45 acp. And i have many questions for you TomBlalock. I do not know how to receive alerts on this website and i have more detailed info that I'd rather not post publicly.

j Michigan on February 10, 2014:

Oh and btw sig p226r with garbage dept issue 9mm subsonic 147 gr hydroshok

j from Michigan on February 10, 2014:

I really appreciate your response and completely understand your skepticism. Is there anyway we can communicate other than through this thread. Please feel free to email me @

TomBlalock (author) from Hickory, NC on February 06, 2014:

That's... slightly insane. I know it can happen, but that's crazy. If I could ask, what caliber cartridge and what firearm were you using? I'll say I'm inherently skeptical, because I'm always skeptical, but if what you're saying is true, then congratulations on surviving and nailing the bad guy. Generally speaking, anyone who brings a vest to a gunfight means serious business. I'd be happy to answer any further questions you have though, if you would like, although I'll make no claim to expertise in the field.

J from Michigan w/o typos on February 06, 2014:

Great article! I'm a police officer and was involved in a shooting that put 8 rounds (1 in heart) and the gunman got back on his feet. It took a 9th round (headshot) to put him down. All this while dealing with the other perp who had a shotgun. I want a round that puts a MF down fast! The shotgun guy had a BP vest and i still severed his femoral artery And shattered his OTHER femur......he lived! But at least i stopped him from shooting at me. I have many questions for you. Please respond TomBlalock and I'll give you my email. I really need your expertise!

J from Michigan on February 06, 2014:

Great article! I'm a police officer and was involved in a shooting that put 8 rounds (1 in heart) and the gunman got back on his feet. It took a 9th round (headshot) too but him down. All this while dealing with the other perp who had a shotgun. I want a round that puts a MF down fast! The shotgun guy had a BP best and i still severed his femoral artery And shattered his OTHER femur......he lived! But at least i stopped him from shooting at me. I have many questions for you. Please respond TomBlalock and I'll give you my email. I really need your expertise!

TomBlalock (author) from Hickory, NC on December 10, 2013:

I don't fire too many from mine, these days, either. I keep it as a wilderness defense option, since we don't really need high caliber weapons here in North Carolina for the wildlife. Chances are, I'll never use it, but I'm a huge fan of deep wilderness hiking, and I'd rather have it than not.

GlockGeek on December 07, 2013:

Thanks a lot TomBlalok. I'm originally from NC although in the Northwest now. The ability to fire .45 super just gives me additional options in the out doors here. I probably won't run more than 100 rounds a year of .45 super through it but having that option is very useful here.

TomBlalock (author) from Hickory, NC on December 06, 2013:

In my personal opinion, Glock GEEK, no. You don't need any of those for a Glock 21 to fire .45 Super or .45 ACP flawlessly. I haven't had any issues with mine since the day I bought it, save for one failure to fire with a standard .45 ACP. That was before my modifications, as well. Since then, it's been smooth sailing.

The buffers are simply a way to reduce stress on the frame from the extra force imparted to the slide. It's a good idea, in all reality, but I haven't heard good things about them. If you're going to give it a try, I'd recommend Wilson's combat buffers, if they still make them.

The magazine spring in particular makes me kind of scratch my head. The cartridge weight is more or less apples to apples, since the dimensions are identical to the original .45 ACP, save with stronger webbing and more modern powder. I don't see why you would need a beefier magazine spring for it.

In summary, my opinion is that no, you don't need the other parts. I certainly haven't, and I've no complaints so far either.

Glock GEEK on December 06, 2013:

Loks like this is over a year old. I was wondering how your firearm was holding up with this conversion. Barrel and recoil spring and guide rod is all that you used. I have seen others say that you need a different firing pin spring, buffer, magazine spring or magazine. Are all of these other parts necessary. I have a new Gen 3 G21

wayne on October 05, 2012:

Hello. I have a Sig P-220 in 45 ACP do you know where I can get the item's to convert the Sig to 45 super ?

Thank you for your time

TomBlalock (author) from Hickory, NC on June 02, 2012:

Honestly, the Glock OEM barrel is very accurate out of the barrel. The KKM has better support, which is good, but mine wasn't fitted by KKM, so it isn't a flawless fit, either. As for accuracy, the KKM is as accurate as I need it to be, and far more accurate than I can manage, at current. So, do I believe there is a difference? Sure, but it is very small, and it will be a long time before I'm good enough to notice it. I still highly recommend it though.

TokarevCzar on June 02, 2012:

Do you notice the kkm barrel shoots more accurately?

TomBlalock (author) from Hickory, NC on May 03, 2012:

Well, with that being the case, is there anything I can do to help you learn more, or is there anything specific you want to know? I'm always happy to discuss just about anything with anyone, so just let me know!

Patricia Scott from North Central Florida on May 03, 2012:

Hi I know like nothing about gun. My son-in-laws uncle has a whole collection. After reading this I am curious and want to learn more. Thanks for sharing thils.

flacoinohio from Ohio on May 02, 2012:

What is the difference between the .45 and the super .45? I use the glock 22 personally, I am more comfortable with the .40 cal. I can use multiple grain ammunition without modifying my weapon.

Related Articles